Hemolymph lipids and flight activity in Helicoverpa zea (Boddie) (lepidoptera: Noctuidae)

In this study the flight activity of female and male Helicoverpa zea (Boddie) moths was observed and compared to hemolymph lipid concentrations. The major male and female H. zea flight activity occurred between simulated dusk (1700) and dawn (0300). Male flight activity was up to 7 times greater than females through 6 days after eclosion except for the 1st day (0.8 times). Females had a unimodal pattern of flight activity, peaking between dusk and 2 h later. Males had a bimodal pattern; one between dusk and 2 h later, and another 3 h after dusk, continuing for h. Prior to dusk, total neutral hemolymph lipids (neutral) of H. zea day 4 moths was 64 μg/μl for males and 48 μg/μl for females. Typical lipid composition in day 4 males prior to flight was 1,2-diacylglycerides (DG) (50% w/w), triacylglycerides (TG) (35%), cholesterol esters (2%), and less than 1% monoacylglycerides and cholesterol. The remainder consisted of free fatty acids (<0.5 μg/μl), and various uncharacterized phospholipids and lipophilic compounds. Hemolymph DG concentration patterns were similar between day 4 males and females, were highest in both sexes prior to, during, and after flight (approximately 32 μg/μl), and then decreased steadily throughout the flight period to approximately 16 μg/ml as flight ceased. Hemolymph TG were lower than DG, but followed the same pattern except at 2100 and 2300. In day 4 males between 2100 and 2300, TG increased to 33 μg/μl which was when DG was lowest (15 μg/μl) and their flight activity was highest. Hemolymph DG decreased (26 to 20 μg/μl) in day 4 females between 2100 and 2300 as TG remained fairly constant (18 μg/μl).     

Effects of nutrition and methoprene treatment upon reproductive diapause in Caloptilia fraxinella (Lepidoptera: Gracillariidae)

Abstract Female Caloptilia fraxinella exhibit a prolonged reproductive diapause immediately post adult emergence in mid‐summer until the next spring when mating, egg development and oviposition on fresh Fraxinus spp. leaflets occur. Factors that effect the termination of reproductive diapause are investigated in this species. Caloptilia fraxinella diapausing adults held in overwintering conditions (2 °C, LD 0 : 24 h) for 24 weeks terminate diapause after placement for 2 weeks in simulated summer conditions (24 °C, LD 16 : 8 h) only if they are provided with 10% sugar water. Exogenous application of the Juvenile Hormone (JH) analogue methoprene to moths in both early‐ (summer) and mid‐ (autumn) reproductive diapause demonstrates that JH affects diapause termination but a carbohydrate nutrition source also mediates mating and vitellogenesis. Mating between moth pairs early in diapause occurs only after treatment with methoprene and provision with sugar water. However, there is no impact of mating on the propensity of females to produce vitellogenic oöcytes. Moths collected in the autumn in mid‐diapause respond in a dose‐dependent fashion to methoprene treatment and the response is greater than that of moths early in diapause collected in the summer. Treatment with methoprene and access to sugar water results in vitellogenic oöcytes in 18.75% of females from mid‐diapause moth pairs treated with 0.01 μg methoprene per insect and in all females from pairs treated at the two highest doses of methoprene (0.1 and 1 μg per insect). Mating occurs only between moths in mid‐diapause treated with the two highest doses of methoprene and these doses induce 91% and 100% mating, respectively. Both control and methoprene‐treated males in mid‐diapause held under summer conditions mate successfully and pass a spermatophore to their methoprene‐treated female partner. These data demonstrate that female C. fraxinella undergo a prolonged reproductive diapause in which termination is dependent on JH and further mediated by a carbohydrate nutrition source. The production of vitellogenic oöcytes is independent of mating. These data also provide evidence that response of moths in diapause to exogenous applications of methoprene differs throughout the diapause period and between male and female C. fraxinella.     

Laboratory tests on mating competition between thiotepa-sterilised and normal males of the potato moth, Phthorimaea operculella (Lepidoptera: Gelechiidae)

Male potato moths less than 24-h-old were sterilised in fumigation chambers in the laboratory with one of three concentrations of thiotepa 0·05, 0·075 and 0·1 g at either 25 or 30°C. Sterile males were associated with untreated virgin males and virgin females in the ratios of 1:1:1, 2:1:1, 4:1:1 and 1:0:1. The sterile and normal male contingents were placed with a single female. The percentage of egg hatch after mating decreased with the increase of concentration and the sterile male ratio. Sterile males were competitive in mating and their longevity was not adversely affected in comparison to the control groups.     

At‐vessel mortality of skates (Rajidae) taken in coastal fisheries and evidence of longer‐term survival

Data on the vigour and at‐vessel mortality (AVM) of 6798 skates (comprising Raja clavata n = 6295; R. brachyura n = 208; R. undulata n = 185, R. montagui n = 98 and R. microocellata n = 12) captured by commercial fishing vessels in the inshore waters of the southern North Sea and English Channel were recorded. AVM in longline fisheries averaged 0·44% across five vessels (0–1·47%), although skates were usually unhooked manually and did not usually pass through a bait‐stripper. AVM in otter trawls averaged 0·76% (0–2·35%), from four vessels fishing with tow durations of <1·5 h (southern North Sea) or 1–4 h (English Channel). No AVM was noted for skates taken as a by‐catch in drift trammel nets (soak times <4 h). Anchored tangle nets resulted in an overall AVM of 2·0–2·7%, but increased from 1·47% (13–28 h soak time) to 6·16% (42–53 h soak time). There were significant differences in the vigour of skates between gears, with R. clavata caught by longline and tangle nets in better condition than those captured by otter trawl or drift trammel net. Similarly, R. undulata caught by tangle net were in better condition than those caught by otter trawl. The vigour of R. undulata was also found to be higher than other skate species for both trawl and tangle net. In total, 5283 skates were tagged with Petersen discs and released, with recapture rates for the various combinations of vessel and gear ranging up to 24·8% for R. clavata. Whilst confirming a degree of post‐release survival, quantitative estimates of post‐release mortality for skates remain unknown.     

THF INFLUENCE OF IRRADIANCE ON THF BIOCHEMICAL COMPOSITION OF THE PRYMNESIOPHYTE ISOCHRYSIS SP. (CLONE T-ISO)1

The effects of irradiance on the biochemical composition of the prymnesiophyte microalga, Isochrysis sp. (Parke; clone T-ISO), a popular species for mariculture, were examined. Cultures were grown under a 12:12 h light: dark (L:D) regime at five irradiances ranging from 50 to 1000 μE·m ²·s^?1 and harvested at late-logarithmic phase for analysis of biochemical composition. Gross composition varied aver the range of irradiances. The highest levels of protein were present in cells from cultures grown at 100 and 250 μE·m ³·s¹, and minimum levels of carbohydrate and lipid occurred at 50 μE·m^?2·s^?1. Because the cell dry weight was reduced at lower irradiances, different trends were evident when results were expressed as percentage of dry weights. Protein percentages were highest at Wand 100 μE·m^?2·s^?1 and carbohydrate at 100 μE·m^?2·s^?1. The composition of amino acids did not differ over the range of irradiances. Glutamate and aspartate were always present in high proportions (9.0–13.5%); histidine. methionine, tryptophan, cystine, and hydroxy-proline were minor constituents (0.0–2.6%). Glucose was the predominant sugar in all cultures, ranging from 23.0% (50 μE·m^?2·s^?1) to 45.0% (100 μE·m^?2·s^?1) of total polysaccharide. No correlation was found between the proportion of any of the sugars and irradiance. The proportions of the lipid class components and fatty acids showed little change with irradiance. The main fatty acids were 14:0, 16:0, 16:1(n-7), 18:1(n-9), 18:3(n-3). 18:4(n-3), 18:5(n-3), and 22:6(n-3). Proportions of 22: 6(n-3) increased, whereas l8:3(n-3). 18:3(n-6). and 18:4(n-3) decreased, with increasing irradiance. Pigment concentrations were highest in cultures grown at 50 μE·m^?2·s^?1, except for fucoxanthin and diadinoxanthin (100 μE·m^?2·s^?1). The concentrations of accessory pigments correlated with chlorophyll a, which decreased in concentration with increasing irradiance. On the basts of biochemical composition, an irradiance of 100 μE·m^?1·s^?1 (12:12 h L:D cycle)for the culture of Isochrysis sp. (clone T-ISO) may provide optimal nutritional value for maricultured animals, although feeding trials are now necessary to substantiate this.     

二化螟的多次交配及其对雌蛾产卵量的影响

【目的】利用性诱防控和监测水稻二化螟Chilo suppressalis的有效性在田间已经得到认可。但雄蛾具有多次交配能力,致使性诱防治二化螟的应用策略一直存在争论。本研究的目的是探索二化螟雄蛾的多次交配及其对雌蛾繁殖力的影响,认识性诱防控害虫的机理。【方法】利用行为学方法调查了雌雄蛾以不同比例配对(1∶1, 4∶1和10∶10)时雄蛾的交配次数和交配持续时间,并结合解剖学方法,观察分析了二化螟雄蛾的交配次数对精巢、交配囊和精包大小以及雌蛾产卵量的影响。【结果】二化螟雌雄蛾按1∶1配对时,交配雄蛾和多次交配雄蛾的比例分别为74.0%和36.0%,平均交配1.7次,首次交配主要发生在0-1日龄,绝大部分具有多次交配能力的雄蛾的首次交配发生在0-1日龄。雌雄蛾按4∶1配对时,交配雄蛾和多次交配雄蛾的比例分别为69.4%和51.3%,平均交配2.1次,显著高于按1∶1配对。雌雄蛾按10∶10配对时,交配雄蛾和多次交配雄蛾的比例分别为65.5%和37.8%,平均交配1.9次。雄蛾第3次交配的持续时间显著长于第1和2次交配,但是交配1-3次雄蛾的精巢体积无显著差异。与不同交配次数雄蛾进行交配的雌...     

Comparative toxicity of the two anti-coagulants, coumatetralyl and warfarin, to wild house-mice (Mus musculus L.)

In comparative tests using individually caged wild house-mice (Mus musculus L.) coumatetralyl at 0·05 % in an oatmeal bait-base was found to be as acceptable as plain bait and as acceptable and as toxic as warfarin at 0·025% (the standard dosage). It was less readily accepted at 0·1 or 0·2% in the same bait-base or at 0·05% in a proprietary bait formulation. In further tests with suspected warfarin-resistant mice, coumatetralyl at either 0·05, 0·1 or 0·2% proved more toxic than warfarin at either 0·025, 0·1 or 0·2% respectively. However, some individuals survived 21 days feeding on each of these concentrations of coumatetralyl and, in field and laboratory trials, 0·05 and 0·1% coumatetralyl baits failed to control warfarin-resistant mouse populations after 3–5 weeks. It is concluded that coumatetralyl is a suitable alternative poison to warfarin for use against mice that are susceptible to anti-coagulants but that it is unlikely to control warfarin-resistant populations effectively.     

An energy budget for juvenile thick-lipped mullet, Crenimugil labrosus (Risso)

A series of experiments were carried out to construct an energy budget for juvenile thick lipped mullet, Crenimugil labrosus Risso. A partial factorial experimental design was used to examine the effects of temperature, fish size and meal size on growth. The maximum ration that the fish were able to ingest completely per day was found to be 0·8, 1·4 and 2·3% wet body weight (b.w.) at 13,18 and 23°C, respectively. Ingested maintenance requirements (M.R.) were estimated to be 137, 205 and 288 cal fish^-1 day^-1 at 13, 18 and 23°C, respectively. At 18deg; C, M.R. varied as 25 W^1.04 cal day^-1, where W= fish weight (g). Growth rate increased with increasing temperature. Maximal conversion efficiency was 21–24% and was achieved closer to the maximum ingested ration with increasing temperature. The relationship between respiration rate and W at 18deg; C for 3-20 g fish is described by: respiration rate (ml O₂ h^-1) = 0·128 W^0.976 The energy cost of apparent specific dynamic action at 18deg; C was found to vary between 5·1% and 23·6% of the calorific value of the ingested meal (1% wet b.w.) , mean (± S.E.)=10·2 ± 2·0%. Post mortem analyses of groups of fish fed 0·2, 0·8 and 1·5% wet b.w. meals showed a significant increase in total lipid and a significant decrease in water content with increasing ratio size. A negative correlation was found between body water content and total lipid (and calories). The mean assimilation efficiency (±s.e.) for 5–10 g mullet at 18deg; C was 73·9 ± 3·6%. The observations reported in this study were brought together to construct an energy budget for juvenile C. labrosus which was found to give a reliable prediction (within 10%) of energy demand and growth under the prevailing experimental conditions. Both gross (K₁) and net (K₂) growth efficiencies, based on energy values, increased with increasing ratio size up to satiation and were independent of temperature. The maximum values of K₁ and K₂ observed were 0·33 and 0·46, respectively. The third order efficiency (K₃) appeared to be independent of temperature and ration size; mean values ranged between 0·66 and 0·84.     

Ozone exposure results in various carry-over effects and prolonged reduction in biomass in birch (Betula pendula Roth)

In the first experiment, saplings of ozone-sensitive and a more tolerant clone of Betula pendula Roth were exposed to ambient ozone (control treatment, accumulated exposure over a threshold 40 nmol mol ^{? 1} (AOT40) exposure of 1·0 μmol mol ^{? 1} h) and 1·5 × ambient ozone (elevated-ozone treatment, AOT40 of 17·3 μmol mol ^{? 1} h) over one growing season, 1996. After over-wintering, the dormant elevated-ozone saplings were transferred to the control blocks and assessed for short-term carry-over effects during the following growing season. In the second experiment, three sensitive, four intermediate and three tolerant clones were grown under ambient ozone (control treatment, AOT40 of 0·5–0·8 μmol mol ^{? 1} h per growing season) and 1·6–1·7 × ambient ozone (elevated-ozone treatment, AOT40 of 18·3–18·6 μmol mol ^{? 1} h per growing season) from May 1994 until May 1996, and were assessed for long-term carry-over effects during growing season 1997, after a 12–16 months recovery period. Deleterious short-term carry-over effects of ozone exposure included reduced contents of Rubisco, chlorophyll, carotenoids, starch and nutrients in leaves, lower stomatal conductance, and decreased new shoot growth and net assimilation rate, followed by a 7·5% (shoot dry weight (DW)), 15·2% (root DW) and 23·2% (foliage area) decreased biomass accumulation and yield over the long term, including a reduced root : shoot ratio. However, a slow recovery of relative growth rates during the following two seasons without elevated ozone was apparent. Several long-lasting structural, biochemical and stomatal acclimation, stress-defence and compensation reactions were observed in the ozone-tolerant clone, whereas in the sensitive clone allocation shifted from growth towards defensive phenolics such as chlorogenic acid. The results provide evidence of persistent deleterious effects of ozone which remain long after the ozone episode.     

豆野螟成虫行为学特征及性信息素产生与释放节律

豆野螟Maruca vitrata (Fabricius)是一种严重的泛热带豆类蔬菜害虫。本文在（29±1）℃、相对湿度75%～80%、光周期14L∶10D条件下研究了豆野螟成虫的羽化、交尾行为以及雌蛾性信息素的释放节律。结果表明：其羽化行为全天可见,在雌蛾中,86%于暗期羽化; 在雄蛾中,73%于暗期羽化。雌雄蛾羽化行为在暗期第4、5和8 h差异达到显著 (t>4; P<0.05)。交尾活动发生在暗期19：00到5：00之间,交尾持续时间最短约为20 min,最长约为90 min,3日龄进入暗期第5 h具有最高的交尾率。1、6和7日龄成虫具有单个交尾高峰,2到5日龄成虫具有两个交尾高峰。同一日龄成虫交尾在暗期前半段平均花费的时间要明显高于在后半段花费的时间。低龄和高龄的成虫用于交尾的时间明显高于中龄的性成熟成虫。成虫的开始交尾时间随着日龄的增加逐渐前移。雄蛾对进入暗期后第5 h和第9 h处女雌蛾的性腺提取物和空气收集性信息素的触角电位反应最强,对 3日龄处女雌蛾的性腺提取物和空气收集性信息素的触角电位反应最强。处女雌蛾田间诱蛾试验表明：23：00-01：00为诱蛾高峰期,3日龄处女雌蛾的诱蛾效果最好。该蛾的羽化、交尾及性信息素产生与释放均存在节律上的一致性。雌蛾的性信息素释放的时间较长,见于整个暗期,然而交尾行为发生时间较短,主要发生于两个交尾高峰之间。     

Nitrogen Fixation During Blooms of Nodularia in Coastal Waters and Backwaters of the Arkona Sea (Baltic Sea) in 1974

Nitrogen fixation was investigated by means of the acetylene reduction method during the development of a water bloom of Nodularia in coastal waters of the Baltic Sea west of the island of Hiddensee and in backwaters showing different degrees of eutrophication. Depending on plankton density, the values found varied greatly. The maximum of nitrogen fixation values found in extremely dense water blooms under special conditions (Baltic Sea, 2250 μg N₂/l · h; Kleiner Jasmunder Bodden, 374 μg N₂/l · h) are up to 10³ times higher than from other parts of the Baltic Sea or from inland waters. The average nitrogenase activity determined for coastal water populations of the Baltic Sea is 2.15 pg N₂/heterocyst · h and that of the inmost backwaters 0.77 pg N₂/heterocyst · h. The relationship between N₂-fixation and nutrient content in water is discussed.     

Laboratory experiments on sugar-beet downy mildew (Peronospora farinosa)

The optimum conditions for Peronospora farinosa betae to produce spores were temperature 8–10 °C and relative humidity 90 % or more, but many spores were produced between 5 and 20 °C and between 80 and 90 % R.H. Most spores were formed in darkness after leaves were exposed to light for 6–8 h. Spores survived exposure to 60 % R.H. for up to 5 days, but were soon killed by temperatures above 20 °C. The germination capacity of spores collected from the field was often very small, but this could not be related to the weather. Most seedlings were infected when inoculated at the growing point and incubated in a saturated atmosphere between 3 and 15 °C for at least 8 h.     

Oviposition Behavior of the Eastern Spruce Budworm Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae)

We documented 13 behaviors associated with oviposition in unfertilized and fertilized spruce budworm moths, Choristoneura fumiferana, by videotaping active moths with a macro lens. Apart from resting, the most pronounced behaviors were probing, drumming + probing, and egg laying. Probing was a bending of the abdomen and extension of the ovipositor to touch the substrate in a rocking, back and forth motion. Drumming + probing involved tapping of the substrate with the pro- and mesothocacic legs with concurrent bending of the abdomen as above. Egg laying was the actual process of egg deposition onto the needle surface of a balsam fir twig. Both the frequency and the duration of these behavioral elements varied depending on the mating status of the female. Unfertilized females exhibited a higher frequency of probing and egg laying. The duration of probing was longer in unfertilized females, while drumming + probing and egg laying were longer for fertilized females. This study is the basis for future work on the chemosensilla associated with the perception of host-plant surface chemicals by ovipositing females.     

The susceptibility of Apodemus agrarius and Rattus losea to the anticoagulant rodenticide,flocoumafen

Flocoumafen had good rodenticidal action against Apodemus agrarius and Rattus losea. The acute oral LD₅₀ for male A. agrarius and R. losea was 1·22 mg kg⁻¹ and 1·36 mg kg⁻¹ respectively. Flocoumafen bait was more toxic to R. losea than to A. agrarius. At bait concentrations of 0·002–0·005%, flocoumafen had a single-feed potency with mortalities of 90–100% for R. losea and 77·8–100% for A. agrarius. Experimental baits prepared using the manufacturing 0·5% master mix of flocoumafen were palatable to both species.     

Characterization and flocculation properties of biopolymeric flocculant (glycosaminoglycan) produced by Cellulomonas sp. Okoh

Aims

Bioflocculant production potential of an actinobacteria isolated from a freshwater environment was evaluated and the bioflocculant characterized.

Methods and Results

16S rDNA nucleotide sequence and BLAST analysis was used to identify the actinobacteria and fermentation conditions, and nutritional requirements were evaluated for optimal bioflocculant production. Chemical analyses, FTIR, 1H NMR spectrometry and SEM imaging of the purified bioflocculant were carried out. The 16S rDNA nucleotide sequences showed 93% similarities to three Cellulomonas species (strain 794, Cellulomonas flavigena DSM 20109 and Cellulomonas flavigena NCIMB 8073), and the sequences was deposited in GenBank as Cellulomonas sp. Okoh (accession number HQ537132 ). Bioflocculant was optimally produced at an initial pH 7, incubation temperature 30°C, agitation speed of 160 rpm and an inoculum size of 2% (vol/vol) of cell density 1·5 × 10⁸ cfu ml^?1. Glucose (88·09% flocculating activity; yield: 4·04 ± 0·33 g l^?1), (NH₄)₂NO₃ (82·74% flocculating activity; yield: 4·47 ± 0·55 g l^?1) and MgCl₂ (90·40% flocculating activity; yield: 4·41 g l^?1) were the preferred nutritional source. Bioflocculant chemical analyses showed carbohydrate, protein and uronic acids in the proportion of 28·9, 19·3 and 18·7% in CPB and 31·4, 18·7 and 32·1% in PPB, respectively. FTIR and 1H NMR indicated the presence of carboxyl, hydroxyl and amino groups amongst others typical of glycosaminoglycan. SEM imaging revealed horizontal pleats of membranous sheets closely packed.

Conclusion

Cellulomonas sp. produces bioflocculant predominantly composed of glycosaminoglycan polysaccharides with high flocculation activity.

Significance and Impact of the Study

High flocculation activity suggests suitability for industrial applications; hence, it may serve to replace the hazardous flocculant used in water treatment.     

EFFECTS OF HARVEST STAGE AND LIGHT ON THE BIOCHEMICAL COMPOSITION OF THE DIATOM THALASSIOSIRA PSEUDONANA1

The marine diatom Thalassiosira pseudonana (Hustedt, clone 3H) Hasle and Heimdal was cultured under three different light regimes: 100 μmol photon · m^?2· s^?1 on 12:12 h light : dark (L:D) cycles; 50 μmol photon · m^?2· s^?2 on 24:0 h L:D; and 100 μmol photon · m^?2· s^?1 on 24:0 h L:D. It was harvested during logarithmic and stationary phases for analysis of biochemical composition. Across the different light regimes, protein (as % of organic weight) was highest in cells during logarithmic phase, whereas carbohydrate and lipid were highest during stationary phase. Carbohydrate concentrations were most affected by the different light regimes; cells grown under 12:12 h L:D contained 37–44% of the carbohydrate of cells grown under 24:0 h L:D. Cells in logarithmic phase had high proportions of polar lipids (79 to 89% of total lipid) and low triacylglycerol (≤10% of total lipid). Cells in stationary phase contained less polar lipid (48 to 57% of total lipid) and more triacylglycerol (22 to 45% of total lipid). The fatty acid composition of logarithmic phase cells grown under 24:0 h L:D were similar, but the 100 μmol photon · m^?2· s^?1 (12:12 h L:D) cells at the same stage contained a higher proportion of polyunsaturated fatty acids (PUFAs) and a lower proportion of saturated and monounsaturated fatty acids due to different levels of 16:0, 16:1(n-7), 16:4(n-1), 18:4(n-3), and 20:5(n-3). With the onset of stationary phase, cells grown at 100 μmol photon · m^?2· s^?1 (both 12:12 and 24:0 h L:D) increased in proportions of saturated and monounsaturated fatty adds and decreased in PUFAs. Concentrations (% organic or dry weight) of 14:0, 16:0, 16:1(n-7), 20:5(n-3), and 22:6(n-3) increased in cells of all cultures during stationary phase. The amino acid compositions of cells were similar irrespective of harvest stage and light regime. For mariculture, the recommended light regime for culturing T. pseudonana will depend on the nutritional requirements of the animal to which the alga is fed. For rapidly growing bivalve mollusc larvae, stationary-phase cultures grown under a 24:0 h L:D regime may provide more energy by virtue of their higher percentage of carbohydrate and high proportions and concentrations of energy-rich saturated fatty acids.     

Persistence of enterohaemorrhagic and nonpathogenic E. coli on spinach leaves and in rhizosphere soil*

Aims: Survival of Escherichia coli O157:H7 and nonpathogenic E. coli on spinach leaves and in organic soil while growing spinach in a growth chamber was investigated. Methods and Results: Spinach plants were maintained in the growth chamber at 20°C (14 h) and 18°C (10 h) settings at 60% relative humidity. Five separate inocula, each containing one strain of E. coli O157:H7 and one nonpathogenic E. coli isolate were applied to individual 4‐week‐old spinach plants (cultivar ‘Whale’) grown in sandy soil. Leaf and soil inocula consisted of 100 μl, in 5 μl droplets, on the upper side of leaves resulting in 6·5 log CFU plant^?1 and 1 ml in soil, resulting in 6·5 log CFU 200 g^?1 soil per plant. Four replicates of each plant shoot and soil sample per inoculum were analysed on day 1 and every 7 days for 28 days for E. coli O157:H7 and nonpathogenic E. coli (by MPN) and for heterotrophic plate counts (HPC). Escherichia coli O157:H7 was not detected on plant shoots after 7 days but did survive in soil for up to 28 days. Nonpathogenic E. coli survived up to 14 days on shoots and was detected at low concentrations for up to 28 days. In contrast, there were no significant differences in HPC from days 0 to 28 on plants, except one treatment on day 7. Conclusions: Escherichia coli O157:H7 persisted in soil for at least 28 days. Escherichia coli O157:H7 on spinach leaves survived for less than 14 days when co‐inoculated with nonpathogenic E. coli. There was no correlation between HPC and E. coli O157:H7 or nonpathogenic E. coli. Significance and Impact of the Study: The persistence of nonpathogenic E. coli isolates makes them possible candidates as surrogates for E. coli O157:H7 on spinach leaves in field trials.     

甜菜夜蛾交配行为和能力

在(27±1)℃,光周期L14∶D10的条件下对甜菜夜蛾I>Spodoptera exigua的交配行为及能力进行了研究。结果表明：成虫在羽化当晚即可进行交配,交配率以羽化后头三个晚上的较高(>82%),但从第4天起则显著下降。成虫一天中的交配时间出现于23:30～05:30之间,交配高峰出现在01:30～02:30和03:00～04:00 之间, 其中以第1高峰的发生频率较高。成虫交配持续时间从22～191 min不等,但以30～60 min的为多(40.8%, n=97), 60～90 min的次之(19.4%),超过180 min的较少(10.2 %)。另外,交配持续时间与蛾龄紧密相关。蛾龄越大,交配持续的时间越长,且差异显著。雄蛾一生的交配能力由1～11次不等,但受性比的影响显著：在性比为1∶1的条件下,雄蛾平均交配次数仅为3.0 次,而在2♀∶1♂至5♀∶1♂时,则增加到5.1～6.0 次。雌蛾交配比例及次数受性比的影响也很大：没有交配的雌蛾比例从1∶1时的8.3%增加到5♀∶1♂时的32%,仅交配一次的比例从16.7%增加到38.7%,而交配≥5 次的比例则从 25%下降到0。最后,对这些结果在甜菜夜蛾防治中应用的可能性进行了讨论。     

Laboratory and field evaluation of flocoumafen for rodent control

A new anticoagulant rodenticide, flocoumafen, at a concentration of 0·005% in the bait in 24 h no-choice and 48 h choice laboratory feeding tests was found to cause 100% mortality of the Indian bush rat Golunda ellioti, the Indian gerbil Tatera indica and the soft-furred field rat Rattus meltada. In field trials in sugar cane and wheat, where these species and the Indian mole rat Bandicota bengalensis and Mus spp. were present, about 65% rodent control was obtained with a single treatment with 0·005% flucoumafen bait at the rate of 1 kg/ha. The performance of a single treatment with flocoumafen was comparable with that of 2·4% zinc phosphide, a conventional acute rodenticide. Unlike zinc phosphide, however, two treatments with a 10-day interval with flocoumafen resulted in significantly higher rodent control compared with the single treatment, indicating the superiority of flocoumafen over zinc phosphide in repeat baiting treatments.     

Reduction of Escherichia coli O157:H7 on radish seeds by sequential application of aqueous chlorine dioxide and dry‐heat treatment

Aims: To assess the effectiveness of sequential treatments of radish seeds with aqueous chlorine dioxide (ClO₂) and dry heat in reducing the number of Escherichia coli O157:H7. Methods and Results: Radish seeds containing E. coli O157:H7 at 5·5 log CFU g^?1 were treated with 500 μg ml^?1 ClO₂ for 5 min and subsequently heated at 60°C and 23% relative humidity for up to 48 h. Escherichia coli O157:H7 decreased by more than 4·8 log CFU g^?1 after 12 h dry‐heat treatment. The pathogen was inactivated after 48 h dry‐heat treatment, but the germination rate of treated seeds was substantially reduced from 91·2 ± 5·0% to 68·7 ± 12·3%. Conclusions: Escherichia coli O157:H7 on radish seeds can be effectively reduced by sequential treatments with ClO₂ and dry heat. To eliminate E. coli O157:H7 on radish seeds without decreasing the germination rate, partial drying of seeds at ambient temperature before dry‐heat treatment should be investigated, and conditions for drying and dry‐heat treatment should be optimized. Significance and Impact of the study: This study showed that sequential treatment with ClO₂ and dry‐heat was effective in inactivating large numbers of E. coli O157:H7 on radish seeds. These findings will be useful when developing sanitizing strategies for seeds without compromising germination rates.